Sect. 14. 297 for such slow variations the effect described under 2. above will be by far the most predominant. In fact, the equipment provides a record of the time derivative of the element in question. 6) Records of the time derivatives of magnetic elements can, however, be obtained in a more direct way by recording directly the electromotive force (e. m. f. ) induced in suitably disposed coils by the variations of the geomagnetic field 10, 11. When a coil with the total winding area F is placed with its axis in the direction of a geomagnetic force component the variation of magnetic induction B with time will produce an electromotive force 1 dB 1 dH e=- coveu,uuFdT=- 'oV~,uQf1oFdT (i). )) . !. . =_to-13~ d(B/y) (1). )a) v em! d(tjs) in the coil. The e. mJ. may be amplified and recorded by means of an oscillograph or on a tape recorder. but more often the coil is used in connection with an ordinary galvanometer and the scale value of, for instance the dl1/dt record, will then - in the same way as the scale value of the magnet variometer treated in Subsect. IX - be dependent on the damping factor IX and on TO/T, where To and T are the oscillation periods for the undamped galvanometer and for the magnetic pulsation respectively. The amplitude recorded will be proportional to the amplification factor I, obtained from Eq. (1).

Inhalt
Introductory Remarks.- Morphology of Magnetic Disturbance.- A. General introduction.- B. Normal geomagnetic variation free from disturbance.- C. Characterization of magnetic disturbance.- D. Gross characteristics of geomagnetic disturbance over the world.- E. Sudden commencement of magnetic storms.- F. Average storm-time variation and disturbance-daily variation of geomagnetic field.- G. Development and decay of magnetic storms.- H. Instantaneous and average disturbance field.- I. Geomagnetic bays and other worldwide disturbances of short duration.- J. Geomagnetic pulsations.- K. Inter-relation among geomagnetic disturbance and associated phenomena, and outline of theoretical interpretation.- General references.- Theoretical Aspects of the Worldwide Magnetic Storm Phenomenon.- A. Introduction.- B. The space environment of Earth.- C. The geomagnetic storm.- D. Confinement and compression of the geomagnetic field.- E. Inflation of the geomagnetic field.- F. Historical development.- General references.- Maßzahlen der erdmagnetischen Aktivität.- A. Einleitung.- B. Die Bartelssche Kennziffer K und daraus abgeleitete Maßzahlen.- C. Andere Aktivitätsmaße.- D. Statistische Aussagen der Maßzahlen über Gesetzmäßigkeiten im Auftreten erdmagnetischer Aktivität und deren Ursache.- Literatur.- Classical Methods of Geomagnetic Observations.- A. Geomagnetic observatories and the recording of variations in the geomagnetic elements.- B. Direct determination of the geomagnetic elements.- General references.- Neuere Meßmethoden der Geomagnetik.- A. Komponentenmessung mit Hilfe von Stabmagneten als Meßelemente in Verbindung mit elektronischen Anzeige- und Regelorganen.- B. Komponentenmessung mit Hilfe von Induktivitäten.- C. Atomphysikalische Feld-Meßmethoden.- D.Informationsverarbeitung im Geomagnetismus.- Three-Component Airborne Magnetometers.- Aeromagnetic Surveying with the Fluxgate Magnetometer.- I. Fluxgate magnetometers.- II. Field survey technique.- III. Discussion of advantages and limitations.- Geophysical Applications of High Resolution Magnetometers.- Abstract.- A. Nuclear magnetometers.- B. Ground applications of optical absorption magnetometers.- C. Airborne and satellite applications of optical absorption magnetometers.- Phénomènes T.B.F. d'origine magnétosphérique.- Bibliographie.- Sachverzeichnis (Deutsch-Englisch).- Subject Index (English-German).- Index (Français).